Messages in this thread | | | Date | Wed, 11 Jul 2012 09:09:28 +0900 | From | Yasuaki Ishimatsu <> | Subject | Re: [RFC PATCH v3 0/13] memory-hotplug : hot-remove physical memory |
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Hi Jiang,
2012/07/11 1:50, Jiang Liu wrote: > On 07/10/2012 05:58 PM, Yasuaki Ishimatsu wrote: >> Hi Christoph, >> >> 2012/07/10 0:18, Christoph Lameter wrote: >>> >>> On Mon, 9 Jul 2012, Yasuaki Ishimatsu wrote: >>> >>>> Even if you apply these patches, you cannot remove the physical memory >>>> completely since these patches are still under development. I want you to >>>> cooperate to improve the physical memory hot-remove. So please review these >>>> patches and give your comment/idea. >>> >>> Could you at least give a method on how you want to do physical memory >>> removal? >> >> We plan to release a dynamic hardware partitionable system. It will be >> able to hot remove/add a system board which included memory and cpu. >> But as you know, Linux does not support memory hot-remove on x86 box. >> So I try to develop it. >> >> Current plan to hot remove system board is to use container driver. >> Thus I define the system board in ACPI DSDT table as a container device. >> It have supported hot-add a container device. And if container device >> has _EJ0 ACPI method, "eject" file to remove the container device is >> prepared as follow: >> >> # ls -l /sys/bus/acpi/devices/ACPI0004\:01/eject >> --w-------. 1 root root 4096 Jul 10 18:19 /sys/bus/acpi/devices/ACPI0004:01/eject >> >> When I hot-remove the container device, I echo 1 to the file as follow: >> >> #echo 1 > /sys/bus/acpi/devices/ACPI0004\:02/eject >> >> Then acpi_bus_trim() is called. And it calls acpi_memory_device_remove() >> for removing memory device. But the code does not do nothing. >> So I developed the continuation of the function. >> >>> You would have to remove all objects from the range you want to >>> physically remove. That is only possible under special circumstances and >>> with a limited set of objects. Even if you exclusively use ZONE_MOVEABLE >>> you still may get cases where pages are pinned for a long time. >> >> I know it. So my memory hot-remove plan is as follows: >> >> 1. hot-added a system board >> All memory which included the system board is offline. >> >> 2. online the memory as removable page >> The function has not supported yet. It is being developed by Lai as follow: >> http://lkml.indiana.edu/hypermail/linux/kernel/1207.0/01478.html >> If it is supported, I will be able to create movable memory. >> >> 3. hot-remove the memory by container device's eject file > We have implemented a prototype to do physical node (mem + CPU + IOH) hotplug > for Itanium and is now porting it to x86. But with currently solution, memory > hotplug functionality may cause 10-20% performance decrease because we concentrate > all DMA/Normal memory to the first NUMA node, and all other NUMA nodes only > hosts ZONE_MOVABLE. We are working on solution to minimize the performance > drop now.
Thank you for your interesting response.
I have a question. How do you move all other NUMA nodes to ZONE_MOVABLE? To use ZONE_MOVABLE, we need to use boot options like kernelcore or movablecore. But it is not enough, since the requested amount is spread evenly throughout all nodes in the system. So I think we do not have way to move all other NUMA node to ZONE_MOVABLE.
Thanks, Yasuaki Ishimatsu
> >> >> Thanks, >> Yasuaki Ishimatsu >> >>> >>> I am not sure that these patches are useful unless we know where you are >>> going with this. If we end up with a situation where we still cannot >>> remove physical memory then this patchset is not helpful. >> >> >> > >
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